There have conventionally been proposed many pneumatic tires having a tread surface in which main grooves extending in the circumferential direction of the tire and lateral grooves extending in the widthwise direction of the tire are properly arranged to thereby improve wet performance (see patent documents 1 and 2, for example).
However, with an increase in consciousness for safety during driving of a vehicle in recent years, it is required to further improve tire performance. In particular, an accident during driving on a wet road surface on a rainy day could lead to a tragedy, and approaches to techniques for its improvement are strongly desired.    Patent Document 1: Japanese Patent Application Kokai Publication HEI 7-285302    Patent Document 2: Japanese Patent Application Kokai Publication HEI 8-230415